Several studies, part of a broad program of research on the psychology and physiology of sleep, are in progress: 1. The effect of age on sleep in rodents is being examined. Young and old rats, mice, and hamsters are being compared on the following parameters: total sleep; distribution of sleep stages; amplitude of EEG slow wave activity; sleep continuity; and amplitude of diurnal rhythm of sleep. 2. A computer based program for the automatic scoring of rat sleep is being developed and is near completion. Results show good agreement among computer scoring, scoring by visual inspection of polygraphy records, and visual inspection of behavior. 3. Studies of sleep deprivation in the rat are aimed at reducing some of the ambiguities of such studies. Hippocampal spikes are being used as a measure of sleepiness; the interaction of diurnal rhythm and sleep rebounds is being examined; the effects of sleep deprivation on specific EEG frequencies are being examined. 4. Individual differences in phasic EMG activity during sleep in humans are being correlated with sleep quality, personality variables, and psychopathology.